The molecular mechanisms regulating niche signal distribution in Drosophila germline stem cell niche.

干细胞具有产生子细胞的显著特性，子细胞保留了干细胞的特性，而另一个子细胞则发生分化。干细胞存在于称为干细胞壁龛的专用细胞微环境中。这些小生境决定了干细胞的身份，维持了干细胞群，并协调了分化细胞的适当稳态生产。果蝇生殖系干细胞（GSCs）是理想的体内干细胞研究模型之一。在雄性和雌性性腺的顶端，GSCs与特殊分化的性腺体细胞（小生境细胞）相关联。这些小生境细胞通过分泌信号分子为gsc生成小生境。虽然这些事实表明，生态位的区域是由这些配体的空间分布来定义的，但调节配体在生态位内分布的分子机制并没有被表征。在这项研究中，我们发现果蝇硫酸肝素蛋白聚糖（HSPGs）是GSC生态位的重要组成部分。果蝇2型glypians是HSPGs的一个亚家族，在雌性和雄性性腺的生态位细胞中表达，是维持GSC所必需的。相反，当glypican在卵巢中异位表达时，我们观察到GSC生态位的扩大。这些结果表明，这些glypicans从分子上定义了生态位区域。

Stem cell posses the remarkable characteristics to produce its daughter cell that retain a stem-cell identity and the other that differentiates. Stem cells reside in dedicated cellular microenvironments termed stem-cell niches. These niches dictate a stem-cell identity, maintain the stem cell population, and coordinate proper homeostatic production of differentiated cells. Drosophila germ line stem cells(GSCs) are one of the ideal models for stem cell study in vivo. In apical tips of both male and female gonads, GSCs associate with specially differentiated somatic gonadal cells, the niche cells. These niche cells generate niches for GSCs by secreting signaling molecules. Although these facts indicate that region of niche is defined by the spatial distribution of these ligands, molecular mechanisms that regulate ligand distribution within the niche is not characterized.In this study, we showed that Drosophila Heparan Sulfate Proteoglycans(HSPGs) are essential components of GSC niche. Drosophila two glypians, a subfamily of HSPGs, were expressed in niche cells of female and male gonads and were required for GSC maintenance. Conversely, when glypican was ectopically expressed in ovaries, we observed expansion of GSC niche. These results showed that these glypicans define niche region molecularly.